[AccessD] "ApplyFilter" hassles

Using Access 2002 – but saving my application in Access 2000 format - I
have been busily creating a form with a bunch of sub forms.  Each sub form
is populated from a field in the main form (e.g. SELECT tbl_Names.* where
tbl_Names.Ref_Dept = frm_Main.cmb_Dept).  This all worked fine on the
machine where I’m busy developing it.

I copied the app across to the target machine – which uses Access 2000 –
and tried to run it.  Whenever it encounters one of these sub forms, I
receive an error 4288 - "You can't use the ApplyFilter action on this
window."

This would be a useful message 
 if it weren’t for the fact that I’m not
using the ApplyFilter action – ANYWHERE!

Anyone seen this before?  Anything I need to be aware of that can fix this?